This invention generally relates to the method and apparatus for folding a continuous web of paper, and particularly relates to what is known in the art as zig-zag folding. A folding apparatus and method of this general type is disclosed in U.S. Pat. No. 3,499,643 which is incorporated herein by reference in its entirety. The present invention is an improvement over that disclosed in said patent and successor folders of the same type.
The basic folding principle and operation of the present invention is generally the same as that disclosed in the referenced patent. However, the present invention represents improvements which substantially increase the speed at which the folder can be made to operate. Because of the cost of labor and equipment, speed is of critical importance. Thus, a substantial increase in speed of such a machine can result in substantial cost savings and increased profits to the company producing business forms and the like. It is common in the industry to which this invention relates to specify machine speed in the number of feet (meters) of web processed per minute by the machine. While prior folders of this type had the capability of operating at speeds up to approximately 800 fpm (243.84 meters per minute) under certain conditions, with the improvements of the present invention the folder is believed to operate under the same conditions at substantially greater speeds.
Folding machines of the general type disclosed herein include an oscillating arm that guides one or more continuous single or multiple ply webs of material such as paper generally downwardly along the arm as the arm oscillates fore and aft about a horizontal transverse axis relative to the direction of web travel as it enters the folder. The arm directs the web alternately between opposed folding assemblies. Each folding assembly has a plurality of gripper means which travel continuously about a preselected path with the gripper means opening and closing as they travel about the path in synchronization with the positioning of the oscillating arm. The synchronization is such that the gripper means while in their open position receive the web fed to them successively and continuously by the oscillating arm, then grip and thus fold the web, and thereafter release the web allowing it to exit downwardly in a folded configuration. After the grippers close to grip the web at the locations of the folds, they maintain their grip at least until the opposite folding mechanism next grips the web to insure a continuous feeding of the web from the oscillating arm. The folded web is held within the closed gripper means as it moves downwardly and then released to continue its downward movement onto a conveyor table or the like. The path of travel of the gripper means is such that the grippers close more positively and rapidly than they open, it being desirable to close the grippers quickly after receiving the web therein from the oscillating arm. These principles and operation are present in the machine disclosed in the referenced patent and successor machines.
The present invention relates to improvements substantially increasing the speed at which the machine may be operated. These improvements lie in the folding assemblies providing faster closing of the grippers, and in the linkage for driving the oscillating arm. With the present invention, the drive for the oscillating arm is substantially stronger and more durable than that previously known, and the folding assemblies provide rapid positive closing of the grippers relative to the position of the oscillating arm as it moves toward the opposite folding assembly, making operation at substantially higher speed possible and reducing set-up time by making synchronization of the folding assemblies and oscillating arm less critical.
Thus, it is a primary object of the present invention to provide a folding apparatus and method of the general type disclosed in the referenced patent and successor machines, but with substantially increased speed capability and with less set-up time required.